Your Friends The Titanosaurs, part 1: Adamantisaurus, Aegyptosaurus, and Ampelosaurus

This is the first in what I plan as a periodic ongoing series. The response from this year's two previous titanosaur posts was better than I expected, especially considering what I thought was some dry subject matter, so if people are liking the big lugs, why not have them around more often? There are certainly plenty of species, and hopefully they don't become overwhelming if they feature once a month or so, when some other topic isn't coming together. The plan is to briefly cover three species in a post, in more or less alphabetical order. For example, in this post we have Adamantisaurus mezzalirai, Aegyptosaurus baharijensis, and Ampelosaurus atacis, taking us from Brazil to Egypt to France. The third species would have been Aeolosaurus colhuehuapensis, but because there are three species of Aeolosaurus I thought it made sense to hold it back and make the next post all Aeolosaurus. The next one would have been Alamosaurus sanjuanensis, but I have other plans for it. Therefore, Ampelosaurus atacis gets the call.

Adamantisaurus mezzalirai

Adamantisaurus mezzalirai is typical of many titanosaurs: it was named in the 21st century, it is from the Upper Cretaceous of South America, it is only known from a few vertebrae, and so far it has not figured to a great extent in publications outside of its original description. This species was described in Santucci and Bertini (2006), on the basis of six anterior caudals and two chevrons (=haemapophyses of their usage). These fossils were first reported in 1959 by Dr. Sérgio Mezzalira, who was honored for his work in the species name. They were discovered in rocks of the Adamantina Formation of the Bauru Group in the Bauru Basin, southern Brazil. The Adamantina Formation has not proven to be the most amenable to dating; I had it as Turonian–Santonian until working on this entry, actually, but changed it to late Campanian–early Maastrichtian based on recent magnetostratigraphic work (Case 2017). The Adamantina Formation is fantastic if you're looking for crocodylomorphs, and not bad for titanosaurs. Of course, with five named titanosaur species, also including Aeolosaurus maximus, "Antarctosaurus" brasiliensis, Gondwanatitan faustoi, and Maxakalisaurus topai, it wouldn't be entirely surprising if some of them proved to be synonyms.

Six caudals and two chevrons can certainly prepare you a place in Titanosauria, where the vertebra is the coin of the realm, but aren't much to permit a warm, sympathetic, multifaceted restoration (although Wikimedia Commons has both an illustration and a sculpture). Mezzalira associated a femur with the caudals, but Santucci and Bertini (2006) did not include it, given differences in size and preservation, and with four other named titanosaurs in the formation this is a good precaution. The caudal vertebrae are well-preserved, articulated, and interpreted as representing the second through seventh caudals, just past the sacrum. They don't seem particularly basal or derived, as titanosaur caudals go, and compare best to what Santucci and Bertini (2006) identified as DGM 1488-R, 'Series B', which we now know as Trigonosaurus pricei (also known under yet another pseudonym: the "Peirópolis titanosaur"). A. mezzalirai has yet to receive significant coverage since its original description.

Aegyptosaurus baharijensis

Aegyptosaurus baharijensis is certainly one of the most obscure dinosaurs, but had its type material not been lost in the World War II bombing of Munich, it would have been one of the best represented titanosaurs for many years. Granted, that kind of thing doesn't shift you too far in the spectrum of obscurity/visibility among dinosaurs, but it beats the alternative, in which A. baharijensis exists as a phantom species, acknowledged in passing. Enough was known, described, and illustrated, though, that new material could be compared, and it is certainly possible that additional specimens of this species may eventually be found. (Perhaps then we would be able to confirm whether it was a lognkosaurian, albeit a small one.)

When A. baharijensis was named in 1932 by Ernst Stromer, its holotype consisted of three partial vertebrae, part of the left scapula, and nine limb bones including the left humerus, ulna, radius, femur, and tibia, and the right ulna, radius, and femur (I'm not quite sure what the ninth was). These fossils had been discovered in October 1911, and were collected from the early-Cenomanian-aged Baharija (or Bahariya) Formation at Gebel el Dist in the northern Bahariya (or Baharija) Oasis in north-central Egypt. The same formation and area also produced the type material of the theropods Bahariasaurus ingens, Carcharodontosaurus saharicus, and Spinosaurus aegyptiacus, also lost in WWII; given nothing sells in dinosaurs quite like giant theropods, they've rather overshadowed A. baharijensis. Reports of A. baharijensis from Niger are based on Lapparent's work from the mid-20th century. Lapparent made some questionable decisions about assigning specimens to species, to put it politely, so I take all of them with a grain of salt.

This is Gebel el Dist, by Ahmedherz on Wikimedia Commons; an evocative place to be finding dinosaurs!

Stromer's 1932 publication takes some work to find if you operate in any other language than German, and if you do get it, it may not do you much good if, like me, your ability to read German is somewhat hampered by a complete inability to read German. Unfortunately, the regrettable absence of its holotype means that no one has been able to publish a thorough revision of A. baharijensis. When A. baharijensis has been mentioned, it is usually in the context of either biostratigraphy or a brief anatomical comparison. Outside of the obligatory capsules in "field guide"/"dictionary"-type books, the most significant post-1932 treatments have been a page or so in Glut (1997) and a couple of paragraphs in the sauropod chapters of both editions of The Dinosauria (McIntosh 1990; Upchurch et al. 2004). A. baharijensis is a bit unusual among titanosaurs for the amount of limb material, and is significant for providing information about the proportions of the limb bones in a single individual (as we'll see going along, several titanosaurs are known from bonebeds, but good luck trying to pick out the individuals among disarticulated fossils). As noted by Stromer (1932) and McIntosh (1990), the humerus:femur ratio is 0.78, the ulna:humerus ratio is 0.75, and the tibia:femur ratio is 0.69. If I told you that the left femur was measured at 129 cm (50.8 in) long (Stromer 1932), which is  modestly sized for a sauropod, you should be able to figure out the other lengths. (Show your work!) The limb bones are also relatively lightly built, at least compared to "Titanosaurus" (McIntosh 1990).

About the most excitement on the A. baharijensis front since 1944 came in the form of Paralititan stromeri, a giant titanosaur from the same formation and area (Smith et al. 2001). (Paralititan itself has never seemed to get as much attention as it could potentially warrant, either, perhaps due to the ongoing discoveries of more complete titanosaurs of comparable size.) The major importance of this article for A. baharijensis was establishing that it was not the same as P. stromeri: the two had rather different scapulae and humeri, based on overlapping material, and P. stromeri reached much much larger sizes, although of course we must always be careful when invoking size to distinguish fossil organisms known from very limited material. Interestingly, as noted by Smith et al., Stromer's sauropod fossils included a very large dorsal vertebra that could well represent Paralititan.

Ampelosaurus atacis

Of the three species in this post, Ampelosaurus atacis has definitely done the best for itself. Being represented by a bonebed certainly helps; Vila et al. (2012) reported the species from a few other localities, but Ampelosaurus atacis is still best-known by far from the fossils found at the original bonebed site, known variously in the literature as Bellevue, C3, and Campagne-sur-Aude. This site is located in the Upper Aude Valley, in the department of Aude, Occitanie, southern France. Dinosaur fossils had been known anecdotally from the valley since the 1870s, but didn't attract scientific interest until the 1980s (Le Loeuff 2005). The Bellevue locality, on the southern boundary of the Blanquette de Limoux vineyard, was first excavated in 1989. The vineyard was the inspiration for the name of the sauropod, which is derived from the Ancient Greek word for "the vine" (the species name comes from the Latin name for the Aude, "Atax") (Le Loeuff 1995).

The Bellevue bonebed has proven quite fruitful, with approximately 500 titanosaur bones known as of Le Loeuff's 2005 paper. Le Loeuff interpreted the collection as entirely A. atacis at that time, but of course it's always important to keep a healthy respect for the deceptive powers of bonebeds. Vila et al. (2012) distinguished two other titanosaurs from the site based on femora: cf. Lirainosaurus astibiae, smaller and more gracile than A. atacis; and an unnamed more robust titanosaur. To further muddy the waters, Díez Díaz et al. (2013) found that the Bellevue femora assigned to cf. Lirainosaurus astibiae lacked some characteristic Lirainosaurus features and did not differ that much from the standard A. atacis femora. Ideally, articulated or at least associated specimens would allow more definitive accounting of the material, and according to Le Loeuff (2005) such a specimen of Ampelosaurus had recently been recovered from the site, but it does not appear to have been scientifically described yet.

The Bellevue site is at the base of the Marnes de la Maurine Member of the Marnes Rouges Inférieures Formation (Le Loeuff 2005). The age of this unit was initially described as early Maastrichtian (Le Loeuff 1995) but has since been hedged into a less specific late Campanian–early Maastrichtian bracket (Díez Díaz et al. 2013; Csiki-Sava et al. 2015). The site is fluvial in origin, and has also produced fossils of plants, invertebrates, gars, turtles, crocodilians, pterosaurs, avian and non-avian theropods, ankylosaurs, and, since this is France near the end of the Cretaceous, the inevitable Rhabdodon (Le Loeuff 2005). At the time, Europe was somewhat less terrestrial than it is now, with shallow seas leading to an archipelago setting. A. atacis is associated with the faunas of southern France and Iberia, as discussed in Díez Díaz et al. (2013) and Csiki-Sava et al. (2015).

A. atacis, barring any bonebed surprises, is the most completely represented European titanosaur to date. Le Loeuff (1995) used three articulated dorsal vertebrae as the holotype of A. atacis, but also attributed to the species another few dozen bones representing most of the bones of the skeleton. Most of the bones were described only briefly at that time, with a more extensive description coming in Le Loeuff (2005). The presence of skull material has been one of the most significant aspects of A. atacis, although only a tooth (Le Loeuff 1995), a braincase, and a partial lower jaw (Le Loeuff 2005) have been described to date. One of the more notable features is the diverse bony armor, with examples of spines, plates, and bulb-like osteoderms; in fact, the osteoderms were described before A. atacis was named (Le Loeuff et al. 1994).  To give you an idea of the body size, Le Loeuff (1995) reported that the femora were between 75 and 115 cm (30 and 45 in) long, and estimated the body length as around 15 m (49 ft); not a "dwarf" sauropod, but certainly not a "titanic" titanosaur. A study of bone histology by Klein et al. (2012) found that A. atacis and several other small- to medium-sized titanosaurs had an unusual bone texture ("modified lamellar bone") which appears to reflect slowed growth and smaller body size (although not directly correlated to insular dwarfism, where small animals evolve from large animals due to limited space). (I wonder if there is a correlation between body size and development/extent of armor in titanosaurs.)

Although not assigned to A. atacis, there is also a braincase from the Lo Hueco bonebed site in Spain which has been described as Ampelosaurus sp. (Knoll et al. 2013). We'll get into this site more when we come to Lohuecotitan pandafilandi.

Figure 1 from Klein et al. 2012. Although we may choose not to trust any particular titanosaur phylogeny over the others, this diagram also gives information about femur length (grouped into size classes and denoted by colors), and shows that Ampelosaurus and Aegyptosaurus were probably of similar size. Lirainosaurus is in there too, falling into the orange band.

References

Case, J. A. 2017. Age of the Adamantina Formation, Upper Bauru Group, Late Cretaceous, Brazil. Journal of Vertebrate Paleontology, Program and Abstracts, 2017:94.

Csiki-Sava, Z., E. Buffetaut, A. Ősi, X. Pereda-Suberbiola, S. L. Brusatte. 2015. Island life in the Cretaceous - faunal composition, biogeography, evolution, and extinction of land-living vertebrates on the Late Cretaceous European archipelago. Zookeys 1–161.

Díez Díaz, V., X. P. Suberbiola, and J. L. Sanz. 2013. Appendicular skeleton and dermal armour of the Late Cretaceous titanosaur Lirainosaurus astibiae (Dinosauria: Sauropoda) from Spain. Palaeontologia Electronica 16(2):19A.

Glut, D. F. 1997. Aegyptosaurus. Pages 83–84 in Dinosaurs: The Encyclopedia. McFarland & Company, Inc., Jefferson, North Carolina.

Klein, N., P. M. Sander, K. Stein, J. Le Loeuff, J. L. Carballido, and E. Buffetaut, E. 2012. Farke, A. A., editor. Modified laminar bone in Ampelosaurus atacis and other titanosaurs (Sauropoda): implications for life history and physiology. PLoS ONE 7(5):e36907. doi:10.1371/journal.pone.0036907.

Knoll, F., R. C. Ridgely, F. Ortega, J. L. Sanz, and L. M. Witmer. 2013. Butler, R. J, editor. Neurocranial osteology and neuroanatomy of a Late Cretaceous titanosaurian sauropod from Spain (Ampelosaurus sp.). PLoS ONE 8:e54991. doi:10.1371/journal.pone.0054991.

Le Loeuff, J. 1995. Ampelosaurus atacis (nov. gen., nov. sp.), un nouveau Titanosauridae (Dinosauria, Sauropoda) du Crétacé supérieur de la Haute Vallée de l'Aude (France). Comptes Rendus de l'Académie des Sciences Paris 321 (series IIa):693–699.

Le Loeuff, J. 2005. Osteology of Ampelosaurus atacis (Titanosauria) from southern France. Pages  115–137 in V. Tidwell and K. Carpenter, editors. Thunder-lizards: the sauropodomorph dinosaurs. Indiana University Press, Bloomington and Indianapolis, Indiana.

Le Loeuff, J., E. Buffetaut, L. Cavin, M. Martin, V. Martin, and H. Tong. 1994. An armoured titanosaurid sauropod from the Late Cretaceous of southern France and the occurrence of osteoderms in the Titanosauridae. Gaia 10:155–159.

McIntosh, J. S. 1990. Sauropoda. Pages 345–401 in D. B. Weishampel, P. Dodson, and H. Osmólska, editors. The Dinosauria. University of California Press, Berkeley, California.

Mezzalira, S. 1959. Nota preliminar sobre as recentes descobertas paleontológicas no Estado de São Paulo, no período 1958–1959. Notas Prévias do Instituto Geográfico e Geológico 2:1–7.

Santucci, R. M., and R. J. Bertini. 2006. A new titanosaur from western São Paulo State, Upper Cretaceous Bauru Group, south-east Brazil. Palaeontology 49(1):59–66.

Smith, J. B., M. C. Lamanna, K. J. Lacovara, P. Dodson, J. R. Smith, J. C. Poole, R. Giegengack, and Y. Attia. 2001. A giant sauropod from an Upper Cretaceous mangrove deposit in Egypt. Science 292(5522):1704–1706.

Stromer, E. 1932. Ergebnisse der Forschungsreisen Prof. E. Stromers in den Wüsten Ägyptens. II. Wirbeltier-Reste der Baharîjestufe (unterstes Cenoman). 11. Sauropoda. Abhandlungen der Bayerischen Akademie der Wissenschaften, Mathematisch-naturwissenschaftliche Abteilung, Neue Folge 10:1–20. [no two bibliographies ever give this citation the same way]

Upchurch, P., P. M. Barrett, and P. Dodson. 2004. Sauropoda. Pages 259–322 in D. Weishampel, P. Dodson, and H. Osmólska, editors. The Dinosauria (2nd ed.). University of California Press, Berkeley, California.

Vila, B., A. Galobart, J. I. Canudo, J. Le Loeuff, J. Dinarès-Turell, V. Riera, O. Oms, T. Tortosa, and R. Gaete. 2012. The diversity of sauropod dinosaurs and their first taxonomic succession from the latest Cretaceous of southwestern Europe: clues to demise and extinction. Palaeogeography, Palaeoclimatology, Palaeoecology 350–352:19–38.